The present invention relates to a compatible alloy comprising polyvinylidene fluoride ("PVDF") and compatible polymers containing imide moieties. Imide containing polymers usually have a higher heat resistance and dimensional stability than PVDF. The greater material strength of an imide polymer is expected to result in the favorable characteristics of increased hardness and abrasion or mar resistance for a PVDF after forming a compatible blend. Increased hardness and abrasion or mar resistance is beneficial to many applications of PVDF blends, including use of PVDF blends in film form or, otherwise, as a coating material.
PVDF has application in the construction industry as an architectural coating because its excellent weatherability provides for long lasting coatings. PVDF is widely used in the chemical processing industry for piping and valves and as lining and coating material for storage tanks and reaction vessels because of its mechanical strength and resistance to chemical degradation. PVDF also possesses desireable electrical properties for use in wire and cables.
PVDF has a glass transition temperature around 45.degree. C. and is a rubbery material in its amorphous state at room temperature. PVDF has high crystallinity in its solid state which results in a high modulus and good mechanical strength. PVDF coatings are generally thermally stable and resistant to weathering and thermal and chemical degradation. For certain applications, optical clarity of PVDF is a significant characteristic. Hardness and abrasion or mar resistance are significant criteria for the performance of PVDF as an architectural coating and in the chemical processing industry.
Blending polymer has been an important industrial approach towards development of polymeric materials. PVDF has been identified as compatible with a few industrial polymers, including the alkyl methacrylate and alkyl acrylates having carbon content on alkyl groups of less than 3. The polymers compatible with PVDF have the common characteristic of high concentrations of C.dbd.O groups, particularly on side chains of the polymer. It is known from prior art that PVDF is compatible with poly(methylmethacrylate) "PMMA"!. See, for example, U.S. Pat. No. 4,770,939. PVDF is compatible with acrylic resins because of hydrogen bonding between C.dbd.O groups of the acrylic resin and the CH.sub.2 groups of the vinylidene fluoride.
It is known in the art that PVDF, blended with an acrylic resin at around a 70:30 ratio by weight of PVDF to acrylic resin; provides optimum material performance with respect to criteria such as adhesion, toughness and optical clarity. PVDF/acrylic resin alloy systems, however, generally have reduced hardness, and abrasion or mar resistance compared to PVDF alone. The reduction in hardness and abrasion or mar resistance serves to limit the application of PVDF blends as a coating material.